The invention relates generally to an improved cutting tool having radially expandable cutter arms for cutting well casing, and more particularly to improved cutting blades on the outer end of the radially expandable cutter arms for engaging the inner periphery of the well casing in cutting relation.
Heretofore cutting tools have been provided for cutting the inner periphery of well casing and having a cutter body with cutter arms pivotally mounted within slots in the cutter body for movement in a radial direction between a retracted position for lowering the tool within the well casing, and a radially expandable extended position in cutting contact with the inner periphery of the well casing. The lower end portions of the cutter arms have also been formed heretofore with blades having cemented carbide cutting fragments or chips secured thereto and forming the cutting edge.
For example, U.S. Pat. No. 3,331,439 dated July 18, 1967, shows a cutting tool having pivotally mounted cutter arms thereon with blades on the lower ends thereof formed with hard cutting material embedded therein. Likewise, U.S. Pat. No. 2,859,943 dated Nov. 11, 1958 shows a cutting tool for well casing having pivoted outer arms with cutter blades thereon having embedded carbide cutting fragments or chips for forming the cutting surface. U.S. Pat. No. 3,195,636 dated July 20, 1965 shows a similar cutting tool with a pivoted cutter arm and a matrix material bonded to the cutting face of the arm and having embedded cutting elements.
Prior cutting tools such as shown in the above patents, when utilized for cutting a well casing, such as a forty-eight (48) inch diameter casing having a wall thickness of one and one-half (11/2) inch, for example, have required around four or five hours in which to complete the cutting operation.